fix small typo in comments

Author: Zuckjet

src/compiler/utilitiesPublic.ts

@@ -311,7 +311,7 @@ namespace ts {
     // nodes like variable declarations and binding elements can returned a view of their flags
     // that includes the modifiers from their container.  i.e. flags like export/declare aren't
     // stored on the variable declaration directly, but on the containing variable statement
-    // (if it has one).  Similarly, flags for let/const are store on the variable declaration
+    // (if it has one).  Similarly, flags for let/const are stored on the variable declaration
     // list.  By calling this function, all those flags are combined so that the client can treat
     // the node as if it actually had those flags.
     export function getCombinedNodeFlags(node: Node): NodeFlags {